JP6011033B2 - Signal separation device and signal separation method - Google Patents

Description

  The present invention relates to a technique for separating an interference communication signal used on a receiving side of a wireless communication apparatus.

  In recent years, in a wireless communication system, improvement in frequency use efficiency is required for effective utilization of limited radio wave resources. For that purpose, it is desirable to transmit a plurality of signals mixed in the same frequency, and the receiver needs a function of easily separating the interference signals. When the radio waves that have interfered with each other arrive from different directions, it is possible to separate the interference signals based on the arrival directions.

For example, Patent Document 1 discloses a technique for performing signal separation by independent component analysis.
Further, Patent Document 2 proposes a method of bidirectional communication at the same frequency in order to improve the bandwidth utilization rate in satellite communication. In this communication method, two ground stations transmit signals in the same band to the same communication satellite, and the communication satellites receive the two signals in a mixed state. Since the interference signal is frequency-converted as it is and transmitted to the ground station by the communication satellite, the ground station cannot perform signal separation based on the arrival direction. Therefore, the ground station uses the transmission signal of its own station as a replica of one of the interference signals, and subtracts this from the received signal to separate the signals of the other stations.

  In contrast to Patent Document 2, Patent Document 3 discloses a signal separation device that generates a replica of a received signal and separates an interference signal. This is based on the difference in signal parameters of a plurality of signals included in the received signal, and the plurality of signals are sequentially separated from the received signal by the passband variable bandpass filter and the equalization determining means according to the extraction order. It is characterized by that. This technique makes it possible to separate and extract signals with a small amount of calculation under the condition that a plurality of signals having different signal parameters share the same frequency for communication.

JP 2008-92363 A US Pat. No. 6,859,641 JP 2007-097103 A

However, the separation means disclosed in Patent Document 3 has a problem that a plurality of signal parameters must be known. Specifically, it is assumed that the signal parameter is notified prior to the start of communication by a radio control signal using a common radio channel as an example (for example, paragraph [0031] in the specification of Patent Document 3). . In other words, it is necessary for the transmission path estimation of Patent Document 3 to notify known information prior to communication and hold the known information on the receiving side. Therefore, when known information is not held or cannot be held on the receiving side, the interference signal cannot be separated on the receiving side.
Accordingly, it is an object of the present invention to provide means for estimating information necessary for separation of interference signals on the receiving side, and to provide a signal separation apparatus and method for realizing signal separation.

One aspect of a signal separation device according to the present invention is a signal separation device that separates an interference signal in which a plurality of signals are mixed in the same frequency, and includes a first symbol rate estimation unit and a first modulation scheme estimation / demodulation unit. , A first decoding unit, an adaptive canceller unit, a replica generation unit, a second symbol rate estimation unit, a second modulation scheme estimation / demodulation unit, and a second decoding unit.
The first symbol rate estimator estimates the symbol rate of the first signal having the highest strength included in the interference signal. The first modulation scheme estimation / demodulation unit estimates a first modulation scheme from a demodulation result obtained by demodulating the first signal based on a symbol rate of the first signal. The first decoding unit demodulates the first signal by the first modulation scheme, and estimates an information sequence of the demodulated first signal. The replica generation unit generates a replica signal of the first signal from the information sequence of the first signal. An adaptive canceller unit subtracts a replica signal of the first signal from the interference signal and outputs a second signal. The second symbol rate estimation unit estimates a symbol rate of the second signal. The second modulation scheme estimation / demodulation unit estimates a second modulation scheme from a demodulation result obtained by demodulating the second signal based on a symbol rate of the second signal. The second decoding unit demodulates the second signal by the second modulation scheme and estimates an information sequence of the demodulated second signal.

  An aspect of the signal separation method according to the present invention is a signal separation method realized by a signal separation device that separates an interference signal in which a plurality of signals are mixed at the same frequency, and is the most intense signal included in the interference signal. Estimating a symbol rate of a first signal having a high frequency, estimating a first modulation scheme from a demodulation result obtained by demodulating the first signal based on a symbol rate of the first signal, Demodulating the first signal according to the modulation method, estimating the information sequence of the demodulated first signal, generating a replica signal of the first signal from the information sequence of the first signal, Subtracting the replica signal of the first signal from the interference signal, outputting the second signal, estimating the symbol rate of the second signal, and based on the symbol rate of the second signal, 2 A step of estimating a second modulation scheme from a demodulation result obtained by demodulating the signal, and a step of demodulating the second signal by the second modulation scheme and estimating an information sequence of the demodulated second signal. .

  According to one aspect of the embodiment of the present invention, it is possible to provide means for estimating information necessary for separation of interference signals on the receiving side, and to provide a signal separation apparatus and method for realizing signal separation.

It is a block diagram which shows the structural example of embodiment of this invention. It is a flowchart which shows the operation example of the signal separation apparatus of 1st Embodiment. FIG. 2 is a block diagram showing a configuration of a symbol rate estimation unit (first symbol rate estimation unit) shown in FIG. 1. It is explanatory drawing of the modulation system estimation part (1st modulation system estimation part) shown in FIG. It is a figure explaining the symbol rate estimation part of 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. In the drawings, components having the same configuration or function and corresponding parts are denoted by the same reference numerals and description thereof is omitted.

Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 1 is a block diagram showing the configuration of the embodiment of the present invention. In this embodiment, the signal demultiplexer includes a symbol rate estimator (first symbol rate estimator) 11, a demodulator (first demodulator) 12, and a modulation scheme estimator (first modulation scheme estimator) 13. , Decoder (first decoder) 14, encoder (first encoder) 15, modulator (first modulator) 16, adaptive canceller 17, symbol rate estimator (second symbol rate estimator) ) 18, a demodulator (second demodulator) 19, a modulation scheme estimator (second modulation scheme estimator) 20, and a decoder (second decoder) 21.

The symbol rate estimation unit 11 receives the interference signal and estimates the symbol rate of the interference signal. Specifically, the symbol rate estimation unit 11 extracts a signal having the highest intensity included in the interference signal from the mixed signal, and estimates the symbol rate of the first signal.
The demodulator 12 demodulates the first signal included in the interference signal using the set modulation method. The set modulation scheme is arbitrary or a modulation scheme estimated by the modulation scheme estimation unit 13. Specifically, when the demodulator 12 receives the first signal extracted by the first symbol rate estimation unit 11, first, the demodulator 12 first uses an arbitrary modulation scheme (a preset modulation scheme) to perform the first signal. Are demodulated and output to the modulation scheme estimator 13. Next, the demodulation of the first signal using the modulation scheme (first modulation scheme) estimated by the modulation scheme estimation unit 13 is repeated. Here, it is assumed that the demodulator 12 holds an arbitrary modulation scheme in advance. Alternatively, the demodulator 12 may be used with reference to an arbitrary modulation method held in a storage area in the signal separation device.

The modulation scheme estimator 13 estimates an optimal modulation scheme from the output result of the demodulator 12 (the demodulated first signal). The estimated result is output to the demodulator 12.
The decoder 14 decodes the first signal demodulated by the demodulator 12 and estimates the information sequence of the first signal.
Here, the demodulator 12 and the modulation method estimation unit 13 constitute a first modulation method estimation / demodulation unit 31. The first modulation scheme estimation / demodulation unit 31 realizes a function of estimating the first modulation scheme from the demodulation result obtained by demodulating the first signal based on the symbol rate of the first signal.

The encoder 15 receives the information sequence of the first signal from the decoder 14 and re-encodes the information sequence of the first signal.
The modulator 16 remodulates the information sequence of the first signal encoded by the encoder 15 to generate a replica signal (a replica signal of the first signal).
Here, the encoder 15 and the modulator 16 constitute a replica generation unit 32. The replica generation unit 32 realizes a function of generating a replica of the first signal from the information sequence of the first signal.
The adaptive canceller 17 subtracts the replica signal from the interference signal. Specifically, the adaptive canceller 17 receives the interference signal and the replica signal of the first signal, subtracts the replica signal from the interference signal, and outputs it as a second signal.

The symbol rate estimation unit 18 estimates the symbol rate of the second signal (the output of the adaptive canceller 17).
The demodulator 19 demodulates the second signal using the set modulation method. The set modulation scheme is arbitrary or a modulation scheme estimated by the modulation scheme estimation unit 20. Specifically, when the demodulator 19 receives the second signal from the second symbol rate estimator 18, first, the demodulator 19 outputs the second signal using an arbitrary modulation scheme (a preset modulation scheme). Demodulate and output to modulation scheme estimation unit 20. Next, it repeats demodulating the second signal using the modulation scheme estimated by the modulation scheme estimation unit 20. The demodulator 19 holds an arbitrary modulation scheme in advance. Alternatively, any modulation scheme held in the storage area in the signal separation device may be used as a reference. The arbitrary modulation method may be the same as or different from the arbitrary modulation method used by the demodulator 12, and may be set in advance according to the signal separation device.

The modulation scheme estimator 20 estimates an optimal modulation scheme from the output result of the demodulator 19 (the demodulated second signal). Then, the estimated result is output to the demodulator 19.
The decoder 21 decodes the second signal demodulated by the demodulator 19 and estimates the information sequence of the second signal.
Here, the demodulator 19 and the modulation method estimation unit 20 constitute a second modulation method estimation / demodulation unit 33. The second modulation scheme estimation / demodulation unit 33 realizes a function of estimating the second modulation scheme from the demodulation result obtained by demodulating the second signal based on the symbol rate of the second signal.

  With the configuration shown in FIG. 1, the signal separation device generates a replica signal based only on the intensity difference between interference signals, and separates the signal by subtracting it from the received signal. Thus, the signal separation device can separate the interference signal without depending on the arrival direction of each signal component. In other words, the signal separation device can separate the interference signal without holding the known information (for example, the signal parameter described in Patent Document 3) necessary for the separation of the interference signal.

Next, the operation will be described. FIG. 2 is a flowchart illustrating an operation example of the signal separation device according to the first embodiment.
In the present embodiment, it is assumed that there is a sufficient intensity difference between signals included in the interference signal. First, the symbol rate estimation unit 11 estimates the symbol rate of the first signal having the highest intensity (S11). The demodulator 12 demodulates the first signal from the symbol rate estimated by the symbol rate estimator 11 by an arbitrary modulation scheme (setting an appropriate modulation scheme in advance) (S12). The modulation scheme estimation unit 13 obtains a mean square error between the demodulated received signal (first signal) and the ideal signal point arrangement set by the receiver (signal separation device) (S13). The demodulator 12 and the modulation scheme estimation unit 13 repeat the processing of steps S12 and S13 while changing the modulation scheme (S14, NO). The modulation scheme estimator 13 compares the mean square error, and determines the modulation scheme with the smallest error as the first modulation scheme as the modulation scheme in which the modulation scheme is correctly estimated (S14, YES). When an appropriate first modulation scheme is estimated, the demodulator 12 outputs the demodulated first signal to the decoder 14.

The decoder 14 performs error correction decoding on the signal demodulated by the final modulation method, thereby estimating a high-quality first information sequence (information sequence of the first signal) related to the first signal (S15). ). The encoder 15 re-encodes the estimated first information sequence, and the modulator 16 re-modulates the re-encoded first information sequence to generate a replica of the first signal (S16). ).
The adaptive canceller 17 estimates the amplitude and phase difference between the first signal component in the interference signal and the replica signal, and corrects the replica signal so that these are minimized (S17). The second signal component is extracted by subtracting the corrected replica signal from the interference signal (S18).

  The extracted second signal component is processed by the symbol rate estimator 18, demodulator 19, and modulation scheme estimator 20 by performing the same processing as the symbol rate estimator 11, demodulator 12, and modulation scheme estimator 13. The rate and modulation method are determined (S19). Further, the error correction decoding is performed by the decoder 21 to estimate a high-quality information sequence (information sequence of the second signal) regarding the second signal (S20).

Next, the operation of the symbol rate estimation unit 11 shown in FIG. 1 will be described with reference to FIG.
FIG. 3 is a block diagram showing a configuration of the symbol rate estimation unit 11. Here, the case of linear modulation will be described as an example. In FIG. 3, a symbol rate estimation unit 11 performs a multiplier 22 that squares an interference signal, an FFT unit (Fast Fourier Transform unit) 23 that performs a Fourier transform on the multiplication result, and a peak detection result of the Fourier transform. The peak detector 24 is configured to perform.
The multiplier 22 squares the interference signal, and the FFT unit 23 performs a Fourier transform on the squared interference signal. As a result, a peak of a frequency corresponding to the symbol rate appears. Thereafter, the peak detector 24 detects the symbol rate by performing peak detection by an appropriate method.
The symbol rate estimator 18 can also be realized by the same configuration as in FIG.

Next, the effect | action in the modulation system estimation part 13 shown in FIG. 1 is demonstrated with reference to FIG.
FIG. 4 is a diagram illustrating the means for estimating the modulation scheme of the modulation scheme estimation unit 13. FIG. 4 shows a received signal demodulated by the demodulator 12 and one of signal point arrangements set in advance in the receiver. In FIG. 4, a signal point arrangement of a QPSK (Quadrature Phase Shift Keying) signal is given as an example. The modulation scheme estimator 13 calculates the mean square error between the demodulated received signal and the ideal signal point, stores the value, and compares them while changing the modulation scheme. In FIG. 4, errors are indicated by black circles and arrows. The signal based on the modulation method when the error is the smallest is determined as the final signal and input to the decoder 14.
The modulation scheme estimation unit 20 is the same as the modulation scheme estimation unit 13.

  As described above, the signal separation device according to the present embodiment is a signal separation device that generates a replica of a received signal and separates an interference signal, and is a symbol rate and a modulation method of the strongest signal included in the interference signal. Means for estimating the information sequence, means for generating a replica of the first signal from the estimated information sequence, means for subtracting the replica of the first signal from the interference signal, and the difference between the interference signal and the replica signal. It is characterized by comprising a means for estimating the symbol rate, modulation scheme, and information sequence of the second signal. With this configuration, when the signal parameters of the interference signal (for example, the symbol rate and the modulation method) are unknown, the arrival direction of each component of the interference signal to a receiver that does not have a replica of the signal component included in the interference signal. Provides a means of separation independent of

(Second Embodiment)
FIG. 5 is a diagram for explaining a second embodiment of the present invention. In the present embodiment, functions of the symbol rate estimation units 11 and 18 will be described. FIG. 5 shows the result of squaring the interference signal and performing a Fourier transform. Further, the horizontal axis represents frequency and the vertical axis represents signal level.
In the case of linear modulation such as PSK (Phase-Shift Keying), a peak of a frequency corresponding to the symbol rate appears in the interference signal that has been subjected to the above processing (square, Fourier transform). That is, when two or more signals are mixed, a plurality of peaks corresponding to each signal appear. In the embodiment of the present invention, the number of crosstalk signals can be determined by detecting the signal level of the peak and the position of the peak. As a result, it is possible to separate interference signals from a plurality of unknown signals.

  As described above, when the signal separation apparatus according to the present embodiment estimates the symbol rate, the interference signal is squared and subjected to Fourier transform, whereby a frequency peak corresponding to the symbol rate appears. The symbol rate and the number of interference signals are detected based on the number of peaks and the level of the peaks.

  As described above, according to each of the above embodiments, in the means for separating a signal by generating a replica of one signal based on only the intensity difference between interference signals and subtracting it from the received signal, the symbol Since the rate can be estimated and the modulation method can be estimated, the interference signal can be separated even in an interference signal whose symbol rate or modulation method is unknown.

  For example, in the transmission path estimation of Patent Document 3, a known signal parameter is notified prior to communication, the transmission path is estimated by using the known signal parameter, a replica of the received signal is generated, and the interference signal is separated. In other words, the receiving side needs a known signal sequence for replica creation. On the other hand, in each of the above embodiments, it is not necessary to notify the known information in advance for the estimation of the information sequence, and it is possible to perform the interference separation on the unknown signal. In other words, in each of the above embodiments, an unknown signal is targeted, and no known information is required on the receiving side, and it is not necessary to transmit information such as signal parameters in advance. Therefore, there is an advantageous effect that it is not necessary to hold extra known information on the receiving side.

Furthermore, when the technique of Patent Document 3 is combined with, for example, a technique for detecting multiple signal components by applying a spreading code to a received signal, a known signal sequence and spreading code are essential on the receiving side. Specifically, for example, when the target signal uses a spreading code based on multiplexing, it is necessary to multiply the received signal by a known spreading code. Therefore, signal separation cannot be realized by a device that does not have known information on the receiving side. On the other hand, in each of the above embodiments, the target signal does not need to be a code-spread signal, and therefore information on a known spreading code is not required on the receiving side. In this patent, only a received signal is used to detect a peak, and a symbol rate of a plurality of multiplexed signals obtained thereby is used. Therefore, in each of the above-described embodiments, it is possible to achieve a unique effect that enables signal separation without using a known signal sequence or spreading code. Specifically, in each of the above embodiments, the interference signal is detected and separated by using the received signal level and the peak obtained by multiplying the received signal.
As described above, in the prior art, there is a problem that some signal parameter is required on the receiving side. However, in each of the above embodiments, the parameter of the signal for the radio wave monitoring service or the like is not limited to the communication field. In this case, an advantageous effect that it can be applied is produced.

  In addition, this invention is not limited to embodiment shown above. Within the scope of the present invention, it is possible to change, add, or convert each element of the above-described embodiment to a content that can be easily considered by those skilled in the art.

11 Symbol rate estimator (first symbol rate estimator)
12 Demodulator (first demodulator)
13 Modulation method estimation unit (first modulation method estimation unit)
14 Decoder (first decoder)
15 Encoder (first encoder)
16 modulator (first modulator)
17 Adaptive canceller 18 Symbol rate estimation unit (second symbol rate estimation means)
19 Demodulator (second demodulator)
20 Modulation method estimation unit (second modulation method estimation unit)
21 Decoder (second decoder)
22 multiplier 23 FFT unit 24 peak detection unit 31 first modulation scheme estimation / demodulation unit 32 replica generation unit 33 second modulation scheme estimation / demodulation unit

Claims (6)

A signal separation device for separating an interference signal in which a plurality of signals are mixed at the same frequency,
First symbol rate estimating means for estimating a symbol rate of the first signal having the highest intensity included in the interference signal;
First modulation scheme estimation / demodulation means for estimating a first modulation scheme from a demodulation result obtained by demodulating the first signal based on a symbol rate of the first signal;
First decoding means for demodulating the first signal by the first modulation scheme and estimating an information sequence of the demodulated first signal;
Replica generating means for generating a replica signal of the first signal from the information sequence of the first signal;
Adaptive canceller means for subtracting a replica signal of the first signal from the interference signal and outputting a second signal;
Second symbol rate estimating means for estimating a symbol rate of the second signal;
Second modulation scheme estimation / demodulation means for estimating a second modulation scheme from a demodulation result obtained by demodulating the second signal based on a symbol rate of the second signal;
Second decoding means for demodulating the second signal by the second modulation scheme and estimating an information sequence of the demodulated second signal;
A signal separation device. The first symbol rate estimating means and the second symbol rate estimating means are:
Multiplication means for squaring the interference signal;
Fast Fourier transform means for performing Fourier transform on the result of multiplication by the multiplication means;
2. The signal separation device according to claim 1, further comprising: a peak detection unit that detects a peak as a result of the Fourier transform performed by the fast Fourier transform unit.   3. The signal separating apparatus according to claim 1, wherein the first symbol rate estimating means extracts the number of the interference signals based on a signal level and a peak number. The first modulation scheme estimation / demodulation means is:
First demodulation means for demodulating the first signal by a plurality of set modulation schemes;
First modulation estimating means for estimating the first modulation scheme from a plurality of first signals demodulated by the first demodulating means,
The first decoding means demodulates the first signal using the first modulation scheme estimated by the first modulation estimation means. A signal separation device according to claim 1. A signal separation method realized by a signal separation device that separates an interference signal in which a plurality of signals are mixed in the same frequency,
Estimating the symbol rate of the strongest first signal contained in the interference signal;
Estimating a first modulation scheme from a demodulation result obtained by demodulating the first signal based on a symbol rate of the first signal;
Demodulating the first signal according to the first modulation scheme, estimating an information sequence of the demodulated first signal,
Generating a replica signal of the first signal from the information sequence of the first signal;
A replica signal of the first signal is subtracted from the interference signal to output a second signal;
Estimating a symbol rate of the second signal;
Based on the symbol rate of the second signal, the second modulation method is estimated from the demodulation result obtained by demodulating the second signal,
A signal separation method for demodulating the second signal by the second modulation method and estimating an information sequence of the demodulated second signal. The estimation of the symbol rate of the strongest first signal included in the interference signal is as follows:
Extract the number of interference signals by signal level and peak number,
6. The signal separation method according to claim 5, wherein the extracted signal having the highest signal level is extracted as the first signal.

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